So proud of Myself today !!!

Tonight, I realised I really could apply wat I have studied.... haha~

Disclaimer: What I am abt to write is my own opinion; it may be wrong, but i tink it should be right. In any case feel free to dispute or correct me... thank you... hee~
I also recalled some principles from http:\\www.howstuffworks.com.


A fren called to ask this question:

How does the changing of car gears affect the properties of the car?


My answer:

1) Understand how a gear works. Gear ratio is a ratio between the number of teeth of the driving pinion and the driven wheel. As such,


No. of teeth on driving pinion : 10
No. of teeth on driven wheel : 20

Gear Ratio is 1:2
The driven wheel will be rotating slower in this case.


No. of teeth on driving pinion : 10
No. of teeth on driven wheel : 5

Gear Ratio is 2:1
The driven wheel will be rotating faster in this case.


In most cases, the changing of gears we are actually changing the driven wheel in the car system.


2) POWER = TORQUE X Angular Velocity

TORQUE can be considered "the ability to do work or to resist work"
Angular Velocity can be considered how fast a driven wheel spins


Assumption: There is no loss in power transmitted over the gears. In other words, POWER is constant in the equation.

Therefore,


For say Gears 1 & 2, a larger driving wheel will be used against the pinion to force the wheel to rotate at a lower speed (lower Angular velocity). According to the equation, therefore, the resultant TORQUE of the system will be very high. In other words, the car can do more work at lower gears... tt is y we often use gear 1 or gear 2 to climb slopes.


Conversely, at higher gears (Gear 4, 5 or even 6), a smaller driven wheel is used; thus, the driven wheel is able to rotate faster. But the car will have lesser TORQUE - tt explains y we have to slow down when we reach a hump. Otherwise, the vehicle will just come to a stall.

3) On normal roads, why do we have to change gears anyway ?

It is impossible to stick to one gear (say gear 3) on the roads and attain 90 kmh speeds becos the high POWER transmitted across the gears will cause the teeth of the gears to fail and break. Tt is y we often know tt blowing ur engine in lower gears will spoil the gearing system.

haha so proud tt I am able to apply wat I have learnt in my MAE course and IA.

8)